Summary of Work: Our main project is based on 221 women who collected daily urine samples during the time they were trying to become pregnant. 199 pregnancies were conceived during this time of close observation, which provides data of unprecedented detail on the events of early human pregnancy. Women in the study provided background information on their reproductive history, patterns of alcohol and tobacco use and other relevant exposures. These women also recorded daily information about menstrual bleeding and intercourse on diary cards. The daily urine samples and records are 98% complete. Assays of the urine samples has provided information on ovulation in each cycle, and an extremely sensitive assay for human chorionic gonadotropin (hCG) detected pregnancy starting around the time of implantation. The hCG assay was polyclonal, and its properties of sensitivity and specificity have never been replicated. Thus, these data remain a unique resource, and have provided a steady stream of new information about the events and processes of early pregnancy. Reproductive hormones can be highly stable in frozen urine, and so we continue to extract new hormone information from these samples. - human reproduction, environmental effects, menstrual cycle, ova, fertilization, luteinizing hormone - Human Subjects & Human Subjects: Interview, Questionaires, or Surveys Only